预留端口避免占用ip

问题描述： 业务遇到这个情况，在重启服务时，出现1986端口被占用而无法启动，非得等该端口释放后才启动成功。

问题分析： 1986端口被该服务器上的客户端随机选取源端口给占用掉了。

解决方案： 使用net.ipv4.ip_local_port_range参数，规划出一段端口段预留作为服务的端口，这种方法是可以解决当前问题，但是会有个问题，端口使用量减少了，当服务器需要消耗大量的端口号的话，比如反代服务器，就存在瓶颈了。最好的做法是将服务监听的端口以逗号分隔全部添加到ip_local_reserved_ports中，TCP/IP协议栈从ip_local_port_range中随机选取源端口时，会排除ip_local_reserved_ports中定义的端口，因此就不会出现端口被占用了服务无法启动。

ip_local_reserved_ports解释如下：ip_local_reserved_ports - list of comma separated rangesSpecify the ports which are reserved for known third-partyapplications. These ports will not be used by automatic portassignments (e.g. when calling Connect() or bind() with portnumber 0). Explicit port allocation behavior is unchanged.

The format used for both input and output is a comma separatedlist of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and10). Writing to the file will clear all previously reservedports and update the current list with the one given in theinput.

Note that ip_local_port_range and ip_local_reserved_portssettings are independent and both are considered by the kernelwhen determining which ports are available for automatic portassignments.

You can reserve ports which are not in the currentip_local_port_range, e.g.:

$ cat /proc/sys/net/ipv4/ip_local_port_range32000 61000$ cat /proc/sys/net/ipv4/ip_local_reserved_ports8080,9148

although this is redunDant. However such a setting is usefulif later the port range is changed to a value that willinclude the reserved ports.

Default: Empty

[warning]注意：内核版本要大于2.6.18-164，否则不支持该参数。[/warning]